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Last of a two-part series

MONTREAL — Look at the condition of the pavement on any local street, and consider this: Some of the asphalt that isn’t good enough to be poured on a provincial highway in Quebec winds up on municipal streets.

The information, which is anecdotal, comes from the Transport Quebec roadwork supervisors who turn away deliveries of sub-standard asphalt on provincial highway work sites around the province, said Michel Paradis, a Transport Quebec engineer responsible for testing and research on asphalt in one of the department’s pavement laboratories in Quebec City.

“It’s sad to say, but it often happens at Transport Quebec that we refuse deliveries of asphalt on our work sites because it doesn’t have the right characteristics or it arrives too cold or there’s some other problem with the load, and truck drivers leave and they’ll use it in a municipality’s (road-paving) contract because there’s no surveillance,” he said.

He added it’s the truckers working for private paving companies who have told the department’s supervisors they would pass on the asphalt to municipal projects.

In light of testimony at the Charbonneau Commission examining corruption in Quebec’s construction industry confirming collusion in many Montreal municipal roadwork contracts, The Gazette sought an expert to understand standards for road paving, how long it’s supposed to last and how an entrepreneur’s hand might help road surfaces prematurely degrade, generating more roadwork.

Paradis tests asphalt that winds up on Transport Quebec highways for its resistance to rutting — the grooves made in the road surface by wheels. He also researches new recipes for asphalt and ways to recycle old asphalt stripped off the road to use as aggregate in new mixes.

The best way to understand paving is to understand that asphalt — the top surface of a road that is poured on at usually 40 to 60 millimetres in thickness — is a recipe.

It’s 95 per cent granular material, such as crushed stone, gravel and sand. The remaining five per cent is asphalt binder, the black petroleum product that acts as the molasses to bind the material together.

A freshly repaved road should last 10 to 15 years, Paradis said.

But how it’s laid is as vital as how it’s made.

“You can make an excellent asphalt in a laboratory, but if the entrepreneur takes it and isn’t handy enough, or doesn’t have enough compactors on the site or it’s too cold or the work is done at night or he waits too long and the compaction is done when the asphalt is already too cold, it leads to weaknesses in the layer of asphalt,” he said. “So the service life should be 10 years, but if it’s poorly laid, it could fall to five years maybe, or six years.”

But the opposite is not true, he added. “If you make bad asphalt in the laboratory, then even if you lay it properly the asphalt at its base is bad so it won’t last.”

Normally, a rut develops at a rate of two millimetres per year, Paradis said. So if the pavement is 10 or 15 years old and it has a 15-millimetre rut, it’s normal wear and tear, he said.

“But if you get a 15-millimetre rut and your pavement was laid two years ago, then something didn’t work somewhere,” he said. “Either the asphalt was no good or it was poorly laid.”

And if it shows that kind of premature degradation, it has to be replaced to ensure motorists can safely use the road, he added.

Paradis described how the service life of well-made asphalt can be prematurely shortened because of the way it’s laid. It’s mostly because of overheating, allowing the asphalt to take on an uneven temperature, or inadequate compaction.

“You can reduce the service life of asphalt by five times if you overheat the asphalt.”

If overheated, the binder in the asphalt mix loses the properties that make the asphalt resistant to cracking, he said.

Paradis said his lab has done research on overheated asphalt. Asphalt that was 2½ years old and had been overheated before being poured showed the same degradation as 15-year-old asphalt, he said. “That’s why overheating asphalt is the worst thing you can do.”

And overheating happens, he said. But Transport Quebec has devised means to control the problem now, he explained.

For example, a site supervisor from the department will measure the temperature of asphalt when the road-paving company delivers it to a work site.

“If, for example, it’s October, and the asphalt plant is 30 kilometres from the work site and your asphalt arrives at 170 C, then it means it was higher when it was at the plant.”

The department can also check the data kept at the plant to find out to what temperature the asphalt was heated, he said.

Moreover, an experienced supervisor can spot a slight but telltale colour change in the asphalt. “You see a little bluish smoke in it (when it has been overheated). When you work long enough in this, you can detect it on sight.”

As well, if there’s no cover on the truck that transports the asphalt, the top of the asphalt mix will cool and form a crust while the rest of it will remain very hot. The paver that it’s fed into can’t blend it enough to make the temperature uniform, he said. The uneven temperature will make the pavement degrade prematurely.

However, the Transport Department now has material transfer vehicles that can re-blend the paving material before going into the paver, he said.

Transport Quebec’s supervisors also now use an infrared camera behind the paver to monitor the different temperatures within the asphalt that’s being poured, using thermography to ensure it’s uniform, he said.

The supervisor measures the thickness of the asphalt not with a ruler or measuring tape, but by calculating the pour rate to figure out the average thickness given the quantity of asphalt that arrives on the site and the surface area it’s to cover.

“It’s also one of the major points that’s controlled,” Paradis said, referring to the thickness that winds up being laid.

Compaction is another important factor, he said. If the asphalt that’s poured isn’t compacted properly, water will be able to seep in and the winter freezing and thawing will degrade the pavement more quickly.

Transport Quebec has norms for each ingredient in the different recipes that are appropriate to the climate and conditions of different regions of the province, Paradis said. The norms are for the quality and size of the stones as much as for the binder, he said.

One of the considerations for the asphalt binder, for example, is choosing one that’s resistant to the heat and humidity of a Montreal summer.

And Transport Quebec sets a higher standard of quality for high-traffic arteries such as the Décarie Expressway, otherwise the greater demand on it would wear it out more quickly than a less-travelled artery, he said. For example, Transport Quebec required steel slag in the granular base of the asphalt that was used to repave the expressway in the early 2000s, he said, because it’s durable and not slippery. It helps resist rutting, he said.

Paradis said he doesn’t have precise examples of where the sub-standard asphalt rejected at Transport Quebec work sites has wound up or how many times it’s happened, but he said Transport Quebec’s site supervisors “advise us of this often.

“Often what we hear is that loads of asphalt that arrive non-conforming on a Transport Quebec work site are transported to other work sites that are less monitored. It arrives at the municipal level.

“It comes up pretty frequently in discussions with (our) work site supervisors.”

Paradis said he believes the difference comes down to budgets for monitoring roadwork.

Various Transport Quebec laboratories are responsible for inspecting roadwork, others for setting norms for different types of mix, he explained.

The department has teams that ensure quality and the best methods for laying the asphalt, employing specialists in road foundations, structure, asphalt and concrete.

It also has a team that follows up annually on each section of provincial highway that gets repaved for the subsequent five to seven years, tracking the rate of the appearance of ruts and its overall degradation.

Transport Quebec has a database of information on the sections of highways that are repaved.

Those databases list the quality of the asphalt, the way it was laid and how it behaved afterward, Paradis said. They also contain video of each section of road, he said.

And Transport Quebec has a battery of site supervisors to inspect the asphalt that arrives and monitor how it’s laid.

Not surprisingly, municipalities don’t have the resources for that level of surveillance, Paradis said.

“Not at all,” he said.

“Montreal and Quebec City have a certain amount of control, which is a bit less than Transport Quebec, a little less regular.

“But when it’s a smaller municipality without the technical staff, without as much means, often it’s the control that often goes out the window. No one will measure the pour rate, the compaction of the surface, check temperatures, if it was well done.”

For the first part of Linda Gyulai’s investigation into municipal paving contracts, click here.

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